package app

import (
	"bytes"
	"os"
	"path/filepath"
	"syscall"

	"github.com/pelletier/go-toml/v2"
)

// UpdateAccessConfig preserves all existing settings, ownership and permissions.
// It never opens the data directory; callers can prepare a candidate while serving.
func UpdateAccessConfig(path, listen string, additions []string, allowLAN bool) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return err
	}
	info, err := os.Stat(path)
	if err != nil {
		return err
	}
	cfg := DefaultConfig()
	if err = toml.NewDecoder(bytes.NewReader(data)).DisallowUnknownFields().Decode(&cfg); err != nil {
		return err
	}
	if listen != "" {
		cfg.Listen = listen
	}
	cfg.AllowLANHTTP = cfg.AllowLANHTTP || allowLAN
	for _, raw := range additions {
		base, e := normalizeAccessURL(raw)
		if e != nil {
			return e
		}
		found := false
		for _, existing := range cfg.accessOrigins() {
			if base == existing {
				found = true
				break
			}
		}
		if !found {
			cfg.AccessURLs = append(cfg.AccessURLs, base)
		}
	}
	if err = cfg.Validate(); err != nil {
		return err
	}
	encoded, err := toml.Marshal(cfg)
	if err != nil {
		return err
	}
	out, err := os.CreateTemp(filepath.Dir(path), ".access-config-*.toml")
	if err != nil {
		return err
	}
	defer os.Remove(out.Name())
	defer out.Close()
	if stat, ok := info.Sys().(*syscall.Stat_t); ok {
		if err = out.Chown(int(stat.Uid), int(stat.Gid)); err != nil {
			return err
		}
	}
	if err = out.Chmod(info.Mode().Perm()); err != nil {
		return err
	}
	if _, err = out.Write(encoded); err != nil {
		return err
	}
	if err = out.Sync(); err != nil {
		return err
	}
	if err = out.Close(); err != nil {
		return err
	}
	return os.Rename(out.Name(), path)
}